NEW HAVEN, Conn. — As police charged a Yale animal-lab technician with murdering a graduate student who worked in his building, a portrait began to emerge Thursday of an unpleasant stickler for the rules who often clashed with researchers and considered the mouse cages his personal fiefdom.

Police charged 24-year-old Raymond Clark III with murder, arresting him at a motel a day after taking hair, fingernail and saliva samples to compare with evidence from the grisly crime scene at Yale’s medical school.

Bail was set at $3 million for Clark, who kept his head down and said, “Yes, your honor,” when asked whether he understood his rights.

The muscular former high school baseball and football player is charged in the death of 24-year-old Annie Le, a pharmacology doctoral student at Yale who vanished Sept. 8. Her body was discovered five days later — on what was to have been her wedding day — stuffed into a utility compartment behind a wall in the basement of the research building where she and Clark worked.

Authorities offered no details about the crime Thursday. They would not discuss a motive, largely because Clark will not talk to police, and would not disclose the DNA test results or how they connected Clark to the slaying.

Clark appeared in court with two public defenders who were new to the case.

Co-workers told police that Clark was a “control freak” who viewed the laboratory and its mice as his territory, according to a law enforcement official who spoke on condition of anonymity because the investigation is ongoing.

The official said police are looking into whether Clark’s attitude led to a deadly workplace confrontation with Le.

The investigator also said authorities do not necessarily need to prove a motive because they have an abundance of strong forensic evidence.

As a technician, Clark’s duties included cleaning mouse cages and the floors of the lab.

Le’s work involved experiments on mice that were part of research into enzymes that could have implications for treatment of cancer, diabetes and muscular dystrophy.

The New York Times reported that Clark at times grew angry if lab workers did not wear shoe covers.

“He would make a big deal of it, instead of just requesting that they wear them,” said a researcher who asked not to be identified.

“He would berate them for minor infractions,” said the researcher. “Everyone enforces rules, but he enforced them in an officious manner.”

ABC News reported that Clark sent a text message to Le on the day she vanished requesting a meeting to discuss the cleanliness of mouse cages in the research lab.

At a news conference Thursday, New Haven Police Chief James Lewis called Le’s death a case of workplace violence. He would not elaborate except to say that reports that the two had a romantic relationship were untrue.

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